Transcript Origins and History of Life

Origins and History of Life
Origin of Life
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Hypothesis of today: inorganic molecules in
Earth’s prebiotic oceans combined to
produce organic molecules  primitive cells.
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Spontaneous orgin
Chemical evolution
Extraterrestrial origin
Divine Creation
Time line
10 billion years – sun, planets
4.6 bya – solar system in place, earth’s
crust
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Atmosphere formed by gravitational field
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Water vapor, nitrogen, carbon dioxide, hydrogen,
methane, ammonia, hydrogen sulfide and carbon
monoxide
3.5 bya – prokaryotic cells
A.I. Oparin, 1920’s
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Russian biochemist
Abiotic synthesis – formation of simple
monomers (AA, sugars) from inorganic
molecules
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Use of energy sources (volcanoes, lightning…)
Primordial soup model
Stanley Miller, 1953
Harold Urey
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Tested primordial soup hypothesis
Produced organic molecules
Polymers evolve
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Sidney Fox – Protein first hypothesis
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Graham Cairns Smith – Clay
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AA polymerize when exposed to heat
proteinoids  microspheres (composed of
proteins but have properties of a cell)
Helpful in causing polymerization of monomers to
produce proteins and nucleic acids
RNA-first hypothesis –
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RNA can be both substrate and an enzyme,
genetic material of viruses
Protocell
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Before true cell
Lipid-protein membrane (liposome), carries on
energy metabolism
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Liposomes – formed double layered bubbles when
in water, may have provided life’s first boundary.
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Chemical evolution  biological evolution
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Figure 19.4, p321
History of Life
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Fossils – remains and traces of past life
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Trails, footprints, bone, shell, teeth
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Paleontology – discovering and studying of
the fossil record
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Sedimentation – weathering and erosion of
rocks  sediment  stratum (layer in a
stratigraphic sequence.
Relative/absolute dating of fossils
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Relative dating – strata of the same age
contain fossils of the same organisms
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Absolute dating – use radioactive dating
techniques, gives actual date of fossil
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Uses half-life of radioactive isotope to stable
element
Use C14 isotope for things that contain organic
matter
Geological Timescale era, period, epoch
Table 19.1
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Precambrian period – 87% of time scale
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4.6 bya – 600 mya
Photosynthesizing organisms, O2 in atmosphere
3.5 bya = prokaryotes
2.7 ozone (oxygen enters)
2.2 eukaryotic
1.4 protists
Paleozoic era
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599 mya – 251 mya
Plants evolve on land – all types evolve
Invertebrates, fish, amphibians, reptiles
3 mass extinctions
Carboniferous period – great coal-forming
forest
Mesozoic
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Triassic, Jurassic and Cretaceous periods
251 mya – 65.5 mya
Flowering plants evolve
First small mammals, Dinosaurs, birds,
placental mammals, modern insects
2 mass extinctions, Dinosaurs 65 mya
Cenozoic
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Tertiary period
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65.5 mya – 2 mya
Flowering plants flourish
Primates to early humans, hominids
Mammal diversity, human evolution begins
Quartenary period
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Present
Modern humans, Homo sapien
Human influence on plants
Factors that influence evolution
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Continental drift – continents are not fixed,
their positions and positions of oceans have
changed
Permian period – 1 land mass  pangaea
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Divided into 2 large land masses
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Laurasia
Gondwana
Then split into continents we know today
Plate tectonics
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Branch of geology
Tectonics – movement of earth’s crust
Earth’s crust is fragmented into slab-like
plates that float on a lower hot mantle layer
Mass Extinctions
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Disappearance of a large number of species
or higher taxonomic groups with an interval of
just a few million years
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At least 5
May be due to
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climate changes
Continental drift
Bolide – asteroid that explodes and produces meteorites
that fall to earth
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Found clay containing high levels of iridium, element found
in asteroids